Heat-cleaning oven timing control



Nov. l2, 1968 G. w. NAGl-:L l 3,410,988

HEAT"CLEANING OVEN TIMING CONTROL 48A QTY] l Hill Nov. l2, 1968 Filed April 28, 196

FIG-8- G. W. NAGEL HEAT-CLEANING OVEN TIMING CONTROL 4 Sheets-Sheet 2 Nov. l2, 1968 Filed April 28, 196e /-SO 78 Y/////////////// /////////////'/V///// HEAT-CLEANING OVEN TIMING CONTROL G. W` NAGEL FIG.9.

4 Sheets-Sheet 5 Nov. l2, 1968 G. w. NAGEL HEAT-CLEANING OVEN TIMING CONTROL 4 Sheets-Sheet 4 Filed April 28, 1966 mwem United States Patent O 3,410,988 HEAT-CLEANING OVEN TIMING CONTROL George W. Nagel, Pittsburgh, Pa., assignor to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Apr. 28, 1966, Ser. No. 546,093 7 Claims. (Cl. 219--412) This invention relates to the type of oven adapted for high temperature cleaning of food soils, and is directed particularly to a timing control particularly adapted for use with an oven door latching and locking arrangement of the general type disclosed in my contemporaneously led U.S. patent application Ser. No. 545,967, filed Apr. 28, 1966, entitled Oven Door Latch and Lock Arrangement.

Both safety requirements and common sense dictate that the oven door of a heat-cleaning type oven be locked shut during the potentially dangerous portions of the heatcleaning cycle, that is, whenever temperatures in the oven cavity are substantially above normal cooking temperatures.

The invention of the above-noted application is concerned with a latching and locking arrangement in which the oven door is latched by physically moving a handle to a position in which the door is mechanically restrained from direct opening before the heat-cleaning cycle temperatures are experienced, and in which the door is locked shut during the high temperature portions of the cycle. The locked shut condition means that the door is latched shut in the sense of being mechanically restrained from direct opening and that the option of cancelling the restraint (which is available while the door is latched only) is not available to the user. It is also considered a practical requirement that the locked condition for the door be automatically effected as the oven temperature rises into the heat cleaning range, and be automatically cancelled when the oven temperature falls below the range. Additionally, means for terminating the application of heat to the oven is required, and that is what this present invention is about.

In general, the object of the invention is the provision of a relatively inexpensive timing arrangement which lends itself to incorporation in a latching and locking arrangement of the general type satisfying the above requirements.

In accordance with one preferred embodiment of the invention I provide, in an oven of heat-cleaning character having means for latching the oven cavity door; circuit means for controlling the heating of the cavity, the circuit means including a normally-closed switch operable to an open position for terminating the heating of the cavity; electrically-powered drive means and means adapted to be driven by the drive means to a position opening the switch after a predetermined drive period; means biasing the driven means to a starting position in which the switch is closed, the biasing means being operable to reset the driven means to the starting position when the driven vmeans are disengaged from the drive means; and means for effecting the engagement and disengagement of the drive means and driven means in response to movement of the door latching means into and out of a latching position, respectively. The drive means is energized when the latch means is moved into a latching position and when the oven selector switch is ON. Accordingly, upon latching7 the drive means is energized and the driven means and drive means are placed in engagement so that after a predetermined lapse of time with the parts in this relationship, the oven heating is terminated by virtue of the driven means causing the switch in the circuit controlling the heating of the oven to open. Then when the latch means is moved to an unlatched position, the drive means and driven means are moved out of engagement permitting the drive means to return to a reset position under the urging of the bias means associated with the driven means. With this arrangement, there is no requirement that once the heat-cleaning cycle begins it must continue to normal termination. In other words, if it is desired to cancel the heat cleaning cycle, this may be done and the timing arrangement will be thereby reset for the initiation later of another cleaning cycle.

In the embodiment according to my noted other patent application, I locate the means for effecting the locking of the oven door at the rear of the range and locate the latching means at the front of the range. Link means extend from the front to the rear to coordinate the functions of the latching and locking means in accordance with the conditions exisiting. I incorporate the principal parts of my timing arrangement in the lock assembly at the rear of the range so that the movement of the link means in accordance with positioning of the latch means correlates the operation of both the lock means and the timing arrangement.

The invention will be described in connection with the accompanying drawing illustrating a currently preferred embodiment by way of example, and wherein:

FIGURE 1 is a side elevational view of a range of the heat cleaning type incorporating the invention;

FIG. 2 is a fragmentary horizontal sectional view corresponding to one taken along the line II-II of FIG. l and illustrating the latching means and the forward part of the link means in an unlatched position;

FIG. 3 is a top View of the latching means similar to FIG. 2 illustrating the relationship of parts when the latching means is in a latching position;

FIG. 4 is a fragmentary horizontal sectional view corresponding to one taken along the line III--III of FIG. l and presenting a top view of the lock assembly and the rear part of the link means with the parts shown in a position corresponding to an unlatched condition;

FIG. 5 is a fragmentary vertical sectional view corresponding to one taken along the line V-V of FIG. 4 and illustrating the relationship of the bolt of the latching means relative to a part of the link means;

FIG. 6 is a schematic view in the nature of a force diagram illustrating the operating relationship of the lat-ching, linking and locking means;

FIG. 7 is a fragmentary, enlarged rear elevation view of the lock assembly and the rear part of the link means located at the rear of the range;

FIG. 8 is a fragmentary end View, partly broken, of the lock assembly as viewed from the right of FIG. 7;

FIG. 9 is a fragmentary plan view of the lock assembly and the rear part -of the link means;

FIG. l0 is a vertical sectional view of a part of a timing mechanism; and

FIG. ll is a schematic view of a currently preferred electrical circuit for a range incorporating the invention.

Range and oven structure (FIG. l

The general exterior appearance of the illustrated domestic cooking range incorporating the invention is conventional. It includes an outer housing supporting a top wall cooking surface 12 and la control panel 14 extending along the top rear of the range. The outer housing encloses a forwardly-open oven cavity 16 provided with top and bottom heating elements and 32, respectively, and various thermostatic means represented by part 34. The oven is adapted to be closed by the hinged drop door 18. A fixed handle 20 extends across the width of the door near its top edge and is used for opening and closing the door during normal cooking operations. An operable handle 22 is mounted closely below the fixed handle. By rotating the handle 22 about a quarter turn, a bolt is turned up to project out of the top edge of the door and engage a keeper assembly 24 mounted on the oven framing structure.

It is noted that the latch means has all its movable parts carried by the door 18. The lock effecting assembly generally designated 26, with parts of the timing mechanism incorporated therein, is located at the rear of the range and is connected to function in accordance with the operation of the latch means by link means generally designated 28.

Latch means-keeper (FIGS. 2-4) The keeper bracket 24 which receives the latch `bolt is mounted on the frame structure 36 which frames the oven cavity front opening. The bracket projects forwardly with the bolt receiving opening 38 located over the top edge of the closed door 18. The bracket 24 comprises two nesting parts, the underlying one being secured by screws 42 to the oven frame structure 36, and the top one being adjustably secured to the underlying one. The forward edge 44 of the keeper opening is .angled relative to the plane of rotation of the bolt 40 to provide a cam surface which the bolt engages when the latching means is operated to a latched position. This pulls the oven door 18 toward a sealed position.

Latch means--operating parts (FIGS. 2-4) The operating parts of the latch means carried 'by the door take the general from of a Z-shaped crank pivotal about the axis of the bight portion 46 which is the connecting shaft between the operating handle 22 and the bolt 40. In an unlatched position with the door closed (FIG. 2), the handle 22 extends horizontally n one direction and the bolt 40 extends horizontally in the opposite direction. When the handle 22 is pushed downwardly at its right end (as viewed facing the oven) toward a latching position, the bolt 40 will be turned upwardly into the keeper opening 38 and move along the camming surface 44. Thus with the latching means in a latched position (FIG. 3), the operating handle 22 points down, and the bolt 40 projects up out of the top edge of the door and up into the keeper opening.

Link means (FIGS. 2-5) In the currently preferred form, the link means generally designated 28 includes: a rearwardly-biased drawbar 48 extending Ibetween the front latch means and rear lock effecting means 26; a bell crank 50 at the front end of the drawbar, the crank having the end of one leg 50h pivotally secured lat 52 to the drawbar, and having the junction of its legs pivotally secured at 54 to the keeper bracket 24; and, a rear link 56 (FIG. 4) having one end pivotally connected to the rear end of the drawbar 48, the link extending at a right angle from the drawbar into the lock assembly structure 26 where it is mounted to pivot about a vertical axis.

The link means tells the lock effecting means 26 what position the latching means is in, and under a condition requiring locking the door obstructs the release of the latch. This works as follows. When the latching means is operated from its unlatched FIG. 2 position to its latched FIG. 3 position, the |bolt 40 turning through the keeper slot 38 engages the leg 50A of the bell crank and turns the bell crank about its pivotal securement 54 to the FIG. 3 position. As the bell crank 50 pivots, its leg 50B pulls the drawbar 48 forwardly to place the extreme forward end 48A in a position to obstruct the movement of the bolt 40 back toward an unlatched position. As is perhaps best seen in FIG. 5, the bolt may not be turned back to an unlatched position until the forward end 48A of the drawbar is retracted.

Latch, link, lock operational relationship (FIG. 6)

The schematic view of FIG. 6 shows in simplified form this operational relationship. When the latching means is turned toward a latched position, bolt 40 turns the bell crank 50 to draw the bar 48 forward against the force of biasing spring `60. The ear `62 at the rear end of the bar bears against the end of a lock pin 64 to deflect it from a centered position. With power available, the solenoid 66 is energized to retract the pin, which then centers itself. This deenergizes the solenoid and the pin moves down past the bar to obstruct the return of the bar to its rearward position. The lock pin is also retractable out of an obstructing position by energization of the solenoid 66. The springs 68 represent forces biasing the lock pin toward engagement with the cooperating parts of the link means, and also biasing the lock pin to a yield-able centered position which permits it to be deected one way and another as the rear end of the link means moves one way and another in accordance with latch movement.

The V-shaped element 70 shown as straddling the lock pin `64 is responsive to movement in either direction of the lock pin to close solenoid switch 72 momentarily when movement of the bar 48 causes fiexure in either way of the lock pin. The thermostatic switch 74 is normally open and closes in response to a high oven temperature indicating a cleaning cycle is Starting. When it closes, the solenoid switch 72 and solenoid y66 are shunted out of the circuit so that the solenoid cannot be energized. In other words, the solenoid is disabled at high temperatures.

The general operation of the latching and locking arrangement may now -be readily appreciated with respect to its operation under various conditions. If the oven door is latched shut in the absence of electrical power to the range, the solenoid 66 does not retract the lock pin 64 away from the ear 62. Hence the pin end moves with the ear rather than moving into an obstructing position as the drawbar 48 is moved forwardly. It will be appreciated then, that, in the absence of electrical power, the door may be latched and unlatched without any locking taking place. With electrical power available, the usual case, as the lock pin is deflected by the ear it causes switch 72 to close momentarily by engaging wire lever 70. The solenoid 66 is energized and the lock pin momentarily retracted as the ear moves forwardly, Upon retraction, the lock pin assumes its undeflected position and is centered relative to wire lever 70. Switch 72 opens, deenergizing the solenoid, and the lock pin springs into an obstructing position relative to the link means. However, the lock pin may be readily moved out of an obstructing position with electrical power still available by simply operating the latch means toward an unlatched position. This permits the biasing spring 60 to draw the bar rearwardly and again vcause energization of the solenoid through deflection of the lock pin in the other direction and closing of switch 72. This retracts the lock pin out of the obstructing position.

However, if the lock pin 64 is in an obstructing position while the oven temperature is in the high heat range, the thermally responsive switch 74 closes and disables the solenoid. Accordingly, the biasing spring 60 is unable to draw the bar 4S rearwardly :against the obstruction of the lock pin which may be deflected rearwardly only to a limited extent in the obstructing position because of the stop 75, even though the limited deliection closes switch 72.

One notable feature of the invention of my noted other patent application is the arrangement of the biasing spring 60 to constitute the sole force for urging the bar 48 rearwardly. No force is exerted by the latching means upon the linkage means to effect the rearward movement of the linkage means. Thus, with the oven door latched and locked, if the user attempts to force the latch to an open position, the latching bolt 40 simply bears against the forward end 48A of the drawbar in a direction at right angles to the normal direction of movement of the drawbar. This force is carried directly through the connection 52 of the drawbar to the bell crank leg 50B, and to the keeper bracket and frame structure of the oven. Since such a force is not carried back to the back assembly through the linkage, the drawbar and the cooperating parts in the locking assembly may be of relatively lightweight material not required to resist large stresses.

Lock effecting means (FIGS. 7-9) The currently preferred arrangement embodying lock effecting means 26 according to the inveintion of my noted application is shown in FIGS. 7-9. A lightweight sheet metal shell 76 serves as a base for carrying a number of the parts concerned with locking. The shell is secured to the .back face of a vertical rear wall 78 spaced rearwardly from the vertical rear wall of the oven liner. Thermal insulation occupies the space between the linear and the rear wall 78. The shell is mounted to this rear Wall for limited pivotal movement about a vertical axis passing approximately through vertically aligned upper and lower fasteners 80. The fasteners extend through spacers 82 which space the shell from the wall 78 to permit the shell to rock slightly about the spacers. This mounting arrangement, contributed by another, is used to compensate for thermal expansion and contraction of the range frame, and to prevent the forward end of the drawbar from being pulled out of the unlatching path of the bolt during the heat cleaning cycle. The compensating arrangement includes an Iarm 84 rigidly connected to two opposite corners of the shell by fasteners 86 (FIG. 7) and a bar 88 connected to the outboard end of the arm. The bar 88 is fixed at its forward end to the keeper assembly and extends rearwardly to its pivotal connection with the outboard end of the arm. The bar is of the same material as the drawbar 48 and preferably is of the same dimensions. For all practical purposes, expansion and contraction of both drawbar 48 and bar 88 will be the same since they are subject to essentially the same temperatures. Accordingly, the shell 76 will rock as required to keep the same vadjusted relationship between the rear link 56 and the operating parts in the locking assembly.

The parts in FIGS. 7-9 which correspond to the parts in the schematic of FIG. 6 carry the same numeral. The locking member 64 takes the form of a pin normally biased downwardly by the helical compression spring 68 which bears against the lower face of the solenoid 66 mounting. The pin is mounted for lateral deflection by a sleeveshaped, tight helical spring 68A. The part 62 which engages the lower end of the locking pin 64 is located at the right end (FIG. 7) of the link extension 56. When ther drawbar 48 is moved forwardly or rearwardly, the linkage extension 56 pivots about the vertical .axis 58 (FIGS. 7-9) formed by several notches (also designated 58) in rearwardly-directed flanges of the shell 76. The forward edge of a vertical run of the extension link 56 seats in these notches.

The right end (FIGS. 7 and 9) of the link extension moves toward the rear (i.e., toward the views of FIG. 7) when the drawbar is pulled forwardly during latching, and conversely moves toward the front when the drawbar retracts during unlatching. A raised shoulder 62A engages the end of the downwardly-biased locking pin 64 and deflects the pin toward the rear when the drawbar is moved forwardly. This carries the locking pin into engagement with the V formed wire 70 and results in closure of switch 72 in series With the solenoid 66. The locking pin is retracted against the bias of spring 68, and assumes a vertical position which again centers it with respect to the wire form V. This permits the switch 72 to again open. The force of the biasing spring 68 then drives the pin downwardly past the link end 62.

The sequence of movements of the locking pin relative to the movement of the end 62 as the link extension 56 is moved between its positions is perhaps best shown in FIG. 8. The solid line representation of the link end 62 and pin 64 corresponds to an unlatched condition. The dashdot showings represent successive positions. As the link end 62 moves to the left as viewed in FIG. 8, the locking pin is deflected to a position 64B by engagement of the shoulder with the end of the locking pin. This deiiection, as explained before, energizes the solenoid momentarily, and the pin takes the centered depressed position 64C. If the link end 62 is moved back toward its Isolid line position, its leading edge eng-ages the end of the locking pin 64 and carries it toward a 64D position. If the solenoid 66 is not then disabled in response to a high oven temperature, the solenoid is `again energized to retract and recenter the pin which then moves down under its .bias onto the link end 62 to move back under the end of the centered pin 64. However, if the solenoid is disabled the end 62 forces the locking pin end over to the 64D position against the edge of a -ange and prevents the return of link end 62 to its solid line position. It is noted that the movement of the link end 62 from the dashed line position to its solid line position is effected by the force of the biasing spring 60 and not by :any force transmitted back through the linkage mechanism from the latching means. However the force movin-g the link end 62 from the solid line position to the broken line position is derived from the latchin-g operation and is in opposition to the force of the biasing spring `60.

When the locking pin 64 descends to a position in which it is not supported by the link end 62, it also closes a normally-open interlock switch 92 in series with other parts which function during the high temperature period.

Timing (FIGS. 7-10) The timing arrangement for terminating the supply of heat to the oven in accordance with this invention is also provided in connection with the lock assembly. A timer motor 94, which may be a simple, inexpensive clock motor, is mounted on the shell 76 and has its output shaft flexibly connected through a helical spring sleeve 98 to a drive shaft 96. The shaft 96 is slidably supported at its left end (FIGS. 7 and 9) in a horizontal slot 100. A tension spring 102 urges the slidable left end of the shaft 96 in a direction toward the front of the range. The output shaft includes a worm-thread drive section 104 (FIG. 9) adapted to be engaged -by a wheel 106 carried 4by the extension link 56 for movement therewith and provided with teeth on its periphery adapted to mesh with the teeth of the worm drive section 104. The function of the timer, timer drive, and wheel is to cause the opening of a normally-closed switch 108 after a predetermined period of engagement of the drive shaft and the wheel, when the door is latched shut. In the current arrangement, the timer drive and wheel are designed so that after one hour of engagement the switch 108 will be opened to terminate the supply of heat.

The structural arrangement of the timer wheel assembly is perhaps best understood from the vertical sectional view of FIG. l0 taken .through the wheel and associated structure. The wheel 106 is mounted for rotation about a bolt 110 which secures it to the link extension 56. A helical return spring 112 has one end pinned to the wheel 106 and the other end connected to the link 56 to exert a force urging the wheel 106 in a counterclockwise direction (as viewed from above) to a start (i.e. rest) position. A U-shaped wire or member 114 is carried at the ends of its legs from the bolt for turning movement relative to the bolt. The wheel 106 includes one or more depending lugs 116 disposed to engage the lower leg of the wire form 114 when the wheel rotates sufficiently in either direction. The bight of the wire form 114 is confined between a stop 118 (FIG. 9) on the one side, and the actuating lever for the switch 108 on the other side.

When the link extension 56 is in an unlatched position, the Wheel 106 is out of engagement with the worm drive section 104, and the return spring 112 urges the wheel 106 in a counterclockwise direction until a depending lug 116 engages a leg of the wire form 114 and is stopped by the wire form engaging the limit flange 118. When the link extension 56 is moved to a latched position, the wheel is carried into engagement with the worm drive section. With the timer 94 energized, the wheel is slowly rotated in a clockwise direction and carries the depending lugs around. After the leading lug engages the lower leg of the wire form 114, it carries the bight portion of the wire form into engagement with the actuating lever of normally-closed switch 108. When switch 108 opens, heat cleaning energization is terminated7 and the timer motor 94 is deenergized. Subsequently, after the oven cooled sufficiently, and as the latch means is operated to an open position, the wheel will be moved back away from the drive worm section 104 and the return spring will act to reset the wheel to its initial position from which it started. With this arrangement, each time the latch means is moved from a latched to an unlatched position, the timing system is reset for a subsequent full cycle, regardless of whether a full or only partial cycle has been completed. The system permits interrupting a cycle at any time since the timing does not lock the controls in a condition requiring completion after a cycle has started.

Overall circuit (FIG. 11)

The relationship of the timing arrangement circuitry to the remainder of the oven circuitry as concerned with a heat cleaning cycle or operation is generally illustrated in FIG. l1. A three-wire power source is indicated by the conductor terminals N, L1 and L2. A stepdown transformer 120 and the timer motor 94 are energized across neutral and L2 when the Clean position contacts 122 of the selector switch are closed, and the latching means have ybeen operated to a latched position to effect closure f the normally open interlock switch 92 engaged by the locking pin 64. The secondary of the transformer 120 provides power through another set of contacts 123 in the selector switch in a Clean position to operate control relay means 124 to a position energizing the top heating element 30 in the oven. Until the temperature in the oven f rises above a level, such as 550 F., normally encountered in cooking, the normally-open lock thermostat switch 74 remains open. Above that temperature, the thermostatic switch-74 closes to shunt out the solenoid 66 and the solenoid switch 72 so that these elements are disabled. Thus, the oven door will be locked shut (since the lock pin 64 cannot be retracted out of the way of the link means) until the switch 74 subsequently opens as the oven temperature falls into the normal cooking range of temperatures. Closing of lock switch 74 also energizes an indicating light and Ventilating fans.

After the latching means have been in a latched position with the selector switch in a Clean position for about an hour, the timer operated switch 108 is opened in the manner previously explained. It is noted that this switch 108 could be placed in the circuit between switch 92 and selector switch element 122 rather than where it is shown. Opening of switch 108 deenergizes the transformer 120 and results in opening the circuit to the element supplying heat to the oven cavity. Then when the oven temperature cools below the set temperature of the lock switch 74, this switch opens and the solenoid 66 may again be energized by operating the latching means toward an unlatched position. Further details as to the functioning of the various parts of the circuit may be found in Kastovich U.S. patent application Ser. No. 552,- 663, entitled Oven and tiled Apr. 26, 1966, a continuation-in-part of Kastovich U.S. patent application Ser. No. 521,932, filed Jan. 20, 1966, now abandoned.

It will be appreciated from the foregoing that the timing system is comprised of elementary, inexpensive parts lending themselves to convenient incorporation in the assembly carrying the lock effecting means, and operable in response to the same link means movement controlling the lock effecting means.

I claim as my invention:

1. ln an oven of heat-cleaning character:

a cavity adapted to be heated to heat-cleaning temperatures;

a door mounted on said oven for closing said cavity;

means for latching said door;

`circuit means for controlling the heating of said cavity,

said circuit means including a switch means operable to a position to terminate the heating of said cavity; electrically-powered drive means Imounted on said oven;

means driven by said drive means to a position causing said switch means to take a position terminating said heating of said cavity after a predetermined drive period; means biasing said driven means to a starting position in which said switch means is positioned to permit said heating of said cavity, said biasing means being disposed to move said driven means to said starting position only when said driven means is disengaged from said drive means; and v means for effecting engagement of and disengagement of said drive means and said driven means in response to movement of said latch means into .and out of the latching position, respectively.

Z. In an oven according to claim 1:

said switch means comprise a normally-closed switch operable to an open position to terminate said heating of said cavity.

3. In an oven according to claim 1:

lock effecting means controlled in accordance with positioning of said latching means and in accordance with oven cavity temperatures;

link means connecting said latching means to said lock effecting means; and

said circuit means includes second, normally-open switch means operable to a closed position for energizing said electrically-powered drive means, and simultaneously conditioning said lock effecting means for subsequent locking in response to a predetermined oven cavity temperature.

4. In an oven according to claim 3 wherein:

said driven means comprises a rotatable gear member carried by said link means for movement therewith. 5. In an oven according to claim 3 wherein: said circuit means includes said electrically-powered drive means in series therein so that operation of said switch means to a position terminating said heating after said predetermined drive period deenergizes said electrically-powered drive means as well as terminating said heating of said cavity. 6. In an oven according to claim 4: said electrically-powered drive means comprises a clock motor driving a Worm drive shaft disposed for engagement with said rotatable gear member; and

means are provided for yield'ably connecting said drive shaft to said motor and biasing said shaft towards said gear member.

7. In that type of heat-cleaning oven including means for manually latching the oven door closed, means for eiecting locking of the door automatically in response to a selected high temperature range in the oven, and link means connecting said latch means to said lock effecting means:

a normally-closed switch operable to an open position for terminating heating of said oven a rotatable gear mounted on said link means for movement therewith, said gear being operable after predetermined rotation to open said switch electrically-powered drive means disposed to engage said gear when said link means is moved to a position corresponding to said latch means being in a latched position means vfor resetting said gear to a start position when locking.

References Cited UNITED STATES PATENTS Eigelbach 292--7 Barber 219-412 Bowling 2,19-412 Martin et al. 219--393 Getman 219-412 BERNARD A. GILHEANY, Primary Examiner.

H. B. GILSON,Assstant Examiner. 

1. IN AN OVEN OF HEAT-CLEANING CHARACTER: A CAVITY ADAPTED TO BE HEATED TO HEAT-CLEANING TEMPERATURES; A DOOR MOUNTED ON SAID OVEN FOR CLOSING SAID CAVITY; MEANS FOR LATCHING SAID DOOR; CIRCUIT MEANS FOR CONTROLLING THE HEATING OF SAID CAVITY, SAID CIRCUIT MEANS INCLUDING A SWITCH MEANS OPERABLE TO A POSITION TO TERMINATE THE HEATING OF SAID CAVITY; ELECTRICALLY-POWERED DRIVE MEANS MOUNTED ON SAID OVEN; MEANS DRIVEN BY SAID DRIVE MEANS TO A POSITION CAUSING SAID SWITCH MEANS TO TAKE A POSITION TERMINATING SAID HEATING OF SAID CAVITY AFTER A PREDETERMINED DRIVE PERIOD; MEANS BIASING SAID DRIVEN MEANS TO A STARTING POSITION IN WHICH SAID SWITCH MEANS IS POSITIONED TO PERMIT SAID HEATING OF SAID CAVITY, SAID BIASING MEANS BEING DISPOSED TO MOVE SAID DRIVEN MEANS TO SAID STARTING POSITION ONLY WHEN SAID DRIVEN MEANS IS DISENGAGED FROM SAID DRIVING MEANS; AND MEANS FOR EFFECTING ENGAGEMENT OF AND DISENGAGEMENT OF SAID DRIVE MEANS OF SAID DRIVEN MEANS IN RESPONSE TO MOVEMENT OF SAID LATCH MEANS INTO AND OUT OF THE LATCHING POSITION, RESPECTIVELY. 